Lecture notes Zen 261 (ZEN261) Vertebrate Biology

Origin of life:
• 3.6 bya
• Vertebrates (500 mya)
• Homo sapiens (165 000 ya)




Characteristic- phylum Chordata
Dorsal, hollow nerve cord
• Chordate nerve cord is hollow (neurocoel) and filled with fluid
• Differentiates into the brain and spinal cord in vertebrates (central nervous system)
Notochord
• Dorsal, flexible rod between nerve cord and gut
• Present in all chordate embryos, persists in adults of some groups
• Replaced in most vertebrates by vertebral column that forms around nerve cord
Pharyngeal slits/pouches
• Used for gas-exchange in vertebrates with gills
• Remain as Eustachian tubes (connect pharynx to middle ear) in terrestrial vertebrates
Post-anal tail
• Posterior elongation of body behind anus
• Contains skeletal elements and muscles
• Function in locomotion of aquatic forms
• Various functions in terrestrial vertebrates if present

,Subphylum Urochordata
• Tunicates
• 1600 spp, Marine
• Adults: sea squirts
• Sessile and filter feeding

Subphylum cephalochordate
• Lancelets; amphioxus
• Small <5cm
• 30 spp, marine, shallows
• Notochord & dorsal nerve cord – throughout life

Subphylum Craniata
• Cranium: cartilage/bone (or both)
• Vertebrata – vertebral column (cartilage/bone)
• Not all members have vertebral column
- Hagfish (infraphyla: Myxinomorphi)
- Other vertebrates (infraphyla; Vertebrata)

Infraphyla: Myxinomorphi
• Hagfish
• Most primitive of craniates
- Eel-like body
- No paired/dorsal fin
- No lateral line system in adults
- Degenerate eyes
• Vertebrate absent

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